改革有机化学实验考查的一些做法

医学院校的有机化学实验不同于一般化学专业,它不以合成实验为主且实验学时少,与此相应的实验考查怎样才能提高学生的分析判断能力呢?做法是以测定未知物为主,通过实验考查学生对化合物性质的掌握程度及对一些基本操作的熟练程度。对于固体样品要求学生先测熔点,然后根据附录给出的熔点范围做官能团性质实验。如为液体样品则分两类,一类是给     

“离子迁移”实验的改进及其实验条件优化*

针对“离子迁移”实验中实验现象不明显、实验操作难度大的问题。采用将CuSO₄、K₂CrO₄与淀粉加工成热的糊状流体,趁热装入U型管,冷却后变成半固体的方法,解决了上述问题。并采用单因素实验法对淀粉的用量、CuSO₄与K₂CrO₄混合物的用量(CuSO₄与K₂CrO₄物质的量之比为1∶1)以及迁移电压等实验条件进行优化。优化后的实验结果显示,离子迁移后形成的区域颜色与半固体淀粉的颜色差别很大,便于学生远距离识别。该方法操作简单、现象明显,有利于一线教师的教学演示和学生的分组实验。     

改进电热法测定弱导热性固体材料比热容的应用型实验

从应用型实验出发,基于电热法的基本原理,自行设计、加工并组装一台改进的比热容测定仪,最后测定了固体物质氯化钠粉末的比热容。与传统量热器相比,单独设计并加装了一根样品管,拓宽了待测样品的范围;将待测弱导热性固体氯化钠样品和导热性较好的锌粉预混合,使待测氯化钠样品各部分温度分布均匀,得到了较为准确的比热容数值0.86 J/(g·K)。通过该实验,有助于学生对比热容有一个初步的认识,提高学生设计和组装实验装置的实践能力。     

基于美国AP化学精编实验开发我国高中化学实验

基于AP（美国大学预修课程）化学实验教学和国内普通高中化学实验教学的实践,对比2者的课程标准,并以具体实验“未知化合物的成分定性分析（固体）”为案例,剖析2者的相似点与不同点,为一线教学的化学教师和国内未来高中化学的教学提供一些参考。     

手持技术数字化实验支持下的“盖斯定律”认知*

在“多重转化、比较建构”认知模型指导下,利用手持技术数字化实验和改进装置,在中学化学教材中“中和热的测定”实验的基础上进行拓展设计,用温度传感器测量3个变化过程的反应热:强碱固体溶解于水、强碱固体与稀盐酸反应以及强碱溶液与稀盐酸反应,并基于“四重表征”理论进行分析,实现对“盖斯定律”的验证,促进对“盖斯定律”的内涵认知。克服了操作烦琐、可视性不佳、实验误差大等问题,有助于在教学中渗透化学核心素养。本研究是对教材内容的补充和拓展,为教师进行“盖斯定律”教学实践提供一定参考。     

希托夫法测定离子迁移数实验的教学改革研究

希托夫法是物理化学实验中测定离子迁移数的传统方法。在教学实践中发现,传统实验装置及操作方法易因待测溶液对流、扩散或人为操作失误等问题导致测定的离子迁移数不准确,因此有必要改进该实验的装置和操作方法。本文提出通过调整测量装置中U型迁移管的玻璃活塞数量,改进装液、溶液收集、滴定操作等实验步骤,降低实验操作难度,增加同批样品的滴定分析次数,提高实验结果的准确性。同时减少近70%的废液产生量,降低了教学成本,减少了环境污染。本研究能够激发学生的实验研究创新意识,促其建立污染物减排的环保观念。     

碱式碳酸铜制备实验的改进

以硫酸铜与氨水的反应原理为基础,对碳酸钠和硫酸铜为反应原料制备碱式碳酸铜实验进行了改进,即CuSO4溶液中滴加氨水,且反应一段时间后用酒精灯加热;并进一步探讨了反应物配比对样品的影响,依据TG曲线、XRD图谱对实验结果进行分析。结果表明：Na2CO3与CuSO4物质的量之比为1.0~1.6时可迅速看到绿色样品,样品均为纯相Cu2（OH）2CO3。改进后,实验耗时少,操作简便,现象明显,成功率高。     

“燃烧条件”探究实验的创新改进

对人教版九年级化学上册第七单元的“燃烧条件”探究实验进行了改进。引入了水浴加热、温度传感器、氮气氛围保护、便携氧气瓶等创新点,改进的实验具有高效性、科学性、环保性。     

以问题驱动培养初中生定量实验能力的实践*——以“测定混有碳酸钠的氯化钠样品中碳酸钠含量”为例

在搭建初中定量实验分析的思维模型的基础上,以“测定混有碳酸钠的氯化钠样品中碳酸钠含量”教学为例,在 “总问题”与“子问题”驱动下,引导初中生逐步建立解决定量实验问题的一般方法,提升对定量实验的设计、评价与改进能力,形成具有迁移价值的关键性能力。     

“焰色反应”实验的创新设计

针对教材中“焰色反应”实验存在的不足,通过对“焰色反应”原理及条件的分析,进行了4大实验创新设计,获得异彩纷呈的实验现象,充分激发了学生的学习积极性,培养对化学的热爱。本课的创新改进实现了对教材内容的二次开发,充分发掘了化学实验的教育功能,让课堂焕发活力。     

有机化学实验双语教学课程体系改革与探索

遵循前沿化、国际化、微型化、绿色化的原则,针对实验基础、基本操作实验、微型合成实验、综合实验4个部分开展有机化学实验双语课程体系改革。在建立双语实验预习制度及完善考核制度的基础上,着力训练学生掌握实验原理、明确实验目的、熟悉实验仪器与试剂及实验过程,并用英语完成实验预习报告。积极引导学生产生对有机化学实验的兴趣和学习专业英语的积极性,培育具有国际化视野、实验技能扎实、专业能力全面的创新人才。     

NMR properties of sedimented solutes

This perspective paper is intended to give some insights into the recently proposed technique of NMR of solutes sedimented by ultracentrifugation in a rotor used for solid state NMR experiments. Sedimented "states" correspond to molecules with very little reorientational capability in extremely concentrated solutions. They provide solid state NMR spectra comparable in quality with those of the best microcrystalline samples. Here we report some experiments to look for chemicals which affect the properties of the sediment, and we show that it is possible to fill the rotor in a true ultracentrifuge and then record the spectra. The latter possibility opens new horizons for NMR of sedimented systems.     

Influence of concentrations of elements upon technetium preconcentration in deposition samples during heating

Technetium volatilization during preconcentration of deposition samples (containing rain and solid matter) with different concentrations of elements was studied by tracer experiments. During evaporation of the samples to dryness, hardly and Tc contained in them was volatilized. However, when the same evaporation experiment was carried out with a deionized water sample, unexpected behaviour of Tc was observed, i.e. a part of the Tc was lost during preparation of the dried-up sample. The major elements, which are present in large amounts in deposition samples, affected Tc stability.     

EQUIP: a worldwide program to ensure the quality of urinary iodine procedures

In 2001 the Centers for Disease Control and Prevention (CDC) established a program, Ensuring the Quality of Urinary Iodine Procedures (EQUIP); to assist laboratories around the world and assess the accuracy of their urinary iodine (UI). CDC designed EQUIP to issue unknown specimens to participating laboratories three times per year. Each laboratory was asked to analyze unknown samples in duplicate on three different days. During the first five rounds of EQUIP, 41 laboratories participated, measuring unknown samples and reporting their results to CDC. CDC used these results to prepare a statistical report for the laboratories. Feedback to the laboratories provided external confirmation regarding performance. As a group, laboratory performance improved; several laboratories made considerable improvement. Several laboratories that showed no improvement have ordered new equipment or are arranging for additional training. EQUIP is a key tool used to support laboratory quality assurance in an effort to eliminate iodine deficiency disorders (IDD) in the world.

Molecularly imprinted polymer for the selective extraction of luteolin from Chrysanthemum morifolium Ramat

In this work, luteolin‐imprinted polymers were prepared by noncovalent precipitation polymerization for the first time. Their structural features and morphologies were analyzed by using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The adsorption experiments revealed that the luteolin‐imprinted polymers presented high selective recognition property to luteolin. The selectivity experiment showed that the adsorption capacity and selectivity of polymers to luteolin was higher than that of three structural analogs, including quercetin, isorhamnetin, and ombuin. Furthermore, an efficient method based on luteolin‐imprinted polymers coupled with solid‐phase extraction was developed for the pretreatment of luteolin from Chrysanthemum morifolium Ramat. The results demonstrated that the luteolin‐imprinted polymers coupled with solid phase extraction method was proven to be a potentially competitive technique for the separation and enrichment of luteolin in complex samples such as Chinese patent medicines and biological samples.     

Time-resolved laser-induced fluorimetry for screening polycylic aromatic hydrocarbons on solid-phase extraction membranes

The potential of solid-phase extraction (SPE) time-resolved laser-induced fluorimetry (TRLIF) is evaluated for screening polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Octadecyl membranes are used with the dual purpose of extracting the pollutants from the water sample and serving as the solid substrate for fluorescence detection. Excitation of fluorescence is performed with a Nd:YAG pumped tunable dye laser pumped with a pulsed source for time-resolving spectral interference. Wavelength time matrices (WTMs) and real time-resolved fluorescence spectra are recorded with a pulsed delay generator, a spectrograph and an intensified charge-coupled device (ICCD). In comparison to SPE solid-matrix luminescence (SML) with conventional instrumentation, this approach provides better limits of detection (LOD) and selectivity. The improvement in LOD is of one order of magnitude, reaching the parts-per-trillion level with 10 ml of water sample. The improvement in selectivity allows the direct determination of target compounds in complex samples. The direct determination of benzo[a]pyrene from a spiked river water sample of unknown composition is presented.     

A Plausible Simultaneous Synthesis of Amino Acids and Simple Peptides on the Primordial Earth

Following his seminal work in 1953, Stanley Miller conducted an experiment in 1958 to study the polymerization of amino acids under simulated early Earth conditions. In the experiment, Miller sparked a gas mixture of CH₄, NH₃, and H₂O, while intermittently adding the plausible prebiotic condensing reagent cyanamide. For unknown reasons, an analysis of the samples was not reported. We analyzed the archived samples for amino acids, dipeptides, and diketopiperazines by liquid chromatography, ion mobility spectrometry, and mass spectrometry. A dozen amino acids, 10 glycine‐containing dipeptides, and 3 glycine‐containing diketopiperazines were detected. Miller’s experiment was repeated and similar polymerization products were observed. Aqueous heating experiments indicate that Strecker synthesis intermediates play a key role in facilitating polymerization. These results highlight the potential importance of condensing reagents in generating diversity within the prebiotic chemical inventory.     

Selective excitation of overlapping multiplets; the application of doubly selective and chemical shift filter experiments to complex NMR spectra

Standard 1D TOCSY and NOE experiments have limitations where signals are severely overlapped. Here, two recently published selective excitation methods are evaluated, the first of which uses a chemical shift selective filter to select a single resonance based on its chemical shift, and the second of which is a doubly selective experiment comprising a 1D TOCSY preparation step and subsequent 1D NOE. We also demonstrate the improvement in spectral quality obtained by the use of the zero quantum filter, which is incorporated into both of these experiments. The application of these different methods of selectively exciting overlapped multiplets, to different types of samples is considered.     

Tetra(diethyl)amide-p-tert-butyl-thiacalix[4]arene in Cone Conformation: Synthesis and Binding Properties with Alkali,Alkaline Earth,Heavy and Transition Metal Ions

Tetra(diethyl)amide-p-tert-butylthiacalix[4]arene 1a in the cone conformation was synthesized and its binding properties towards a large variety of metal ions were established on the basis of liquid–liquid and solid–liquid extraction as well as complexation experiments. This compound is a less efficient and selective compound than the “classical” tetra(diethyl)amide-p-tert-butylcalix[4]arene 3 in the cone conformation for alkali and alkaline earth metal ions. However, Pb²⁺ is selectively extracted and complexed within heavy and transition metal ions.